Calibration circuit and antenna device

Abstract

To provide a distributor used in a calibration circuit, which is capable of obtaining good VSWR characteristics on both the branch line side and the merging line side.SOLUTION: A mixing distributor uses a plurality of two-way distributors to form a tournament-type parallel power feed structure of two or more stages. A coupler is provided on each of a plurality of branch lines branched by the mixing distributor. The mixing distributor uses a Wilkinson-type one-stage transformer as two-way distributor that is arranged in the first stage of the tournament-type parallel power feed structure and connected to the branch lines, and uses a Wilkinson-type two-stage transformer as a two-way distributor that is arranged in the final stage of the tournament-type parallel power feed structure and connected to the merged lines merged into one by the mixing distributor.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to techniques for calibrating signals transmitted and received by an antenna. [Background technology]

[0002] An array antenna that performs beam forming is provided with a calibration circuit for calibrating the phase between antenna elements. The calibration circuit includes a plurality of coupling circuits that acquire signals from the respective antenna elements, and a distributor that mixes the signals acquired in the coupling circuits and distributes the calibration signal to each of the coupling circuits.

[0003] For example, the following Patent Document 1 describes a distributor that divides one signal into eight by connecting seven two-way distributors to form a three-stage tournament-type parallel power supply structure. A Wilkinson distributor is used for the two-way distributor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-108741 A Summary of the Invention [Problem to be solved by the invention]

[0005] A signal distributor used to distribute signals to an array antenna is designed to obtain good voltage standing wave ratio (VSWR) characteristics on the branch line side to which the antenna is connected. However, a calibration distributor used in a calibration circuit is required to have good VSWR characteristics not only on the branch line side but also on the junction line side. When a signal distributor is applied to a calibration circuit, a problem was found in which it was not possible to obtain the VSWR characteristics required on the junction line side.

[0006] One aspect of the present disclosure is a distributor used in a calibration circuit, which makes it possible to obtain good VSWR characteristics on both the branch line side and the merging line side. [Means for solving the problem]

[0007] One aspect of the present disclosure is a calibration circuit, comprising a mixer / distributor and a plurality of couplers. The mixer / distributor is configured to form a two or more stage tournament-type parallel power feed structure using a plurality of two-way dividers. The couplers are provided on each of a plurality of branch lines branched by the mixer / distributor. The couplers are configured to separate a part of a signal flowing through a main signal line from each of the main signal lines transmitting signals transmitted and received by a plurality of antenna elements forming an array antenna, or to mix a calibration signal with a signal flowing through the main signal line. The mixer / distributor is disposed in the first stage of the tournament-type parallel power feed structure and uses a Wilkinson type one-stage transformer as a two-way divider connected to the branch line. The mixer / distributor is disposed in the final stage of the tournament-type parallel power feed structure and uses a Wilkinson type two-stage transformer as a two-way divider connected to a junction line joined together by the mixer / distributor.

[0008] With this configuration, good VSWR characteristics can be obtained on both the branch line side and the merging line side.

[0009] One aspect of the present disclosure is an antenna device comprising a plurality of antenna elements forming an array antenna and the above-described calibration circuit. With this configuration, the calibration accuracy of the transmission and reception signals in the antenna device can be improved. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram showing a configuration of an antenna device. [Diagram 2] FIG. 4 is a pattern diagram showing wiring of a calibration circuit. [Diagram 3]This is a pattern diagram of a Wilkinson type two-stage transformer. [Figure 4] FIG. 1 is a pattern diagram of a coupler. [Diagram 5] 13 is a graph showing simulation results of VSWR characteristics as viewed from a merging line side and two branching line sides for a single-stage transformer alone and a two-stage transformer alone. [Figure 6] 13 is a graph showing simulation results of VSWR characteristics as viewed from each of the merging line side and the branching line side in a comparative example of a mixing distributor in which Wilkinson type two-stage transformers are used as all two-way dividers that make up the mixing distributor. [Figure 7] 11 is a graph showing simulation results of VSWR characteristics as viewed from the merging line side and the branching line side in the mixing distributor of the embodiment. [Figure 8] 11 is a graph showing the results of measuring VSWR characteristics as viewed from the merging line side and the branching line side in the mixing distributor of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. [1. Configuration] The antenna device 1 shown in Fig. 1 is used for transmitting and receiving high-frequency signals. The antenna device 1 is used, for example, as a base station antenna for mobile phones.

[0012] The antenna device 1 includes an antenna section 2, a calibration circuit 3, an antenna control section 4, and a calibration control section 5. The antenna unit 2 includes eight antenna elements 21 to . The antenna elements 21 to are radiating elements that transmit and receive high-frequency signals, and may be, for example, patch antennas. The antenna elements 21 to are arranged, for example, in a row at equal intervals. The antenna elements 21 to function as a phased array antenna that operates by receiving power from the calibration circuit 3 and forms a radiation pattern according to the excitation state.

[0013] The calibration circuit 3 includes signal ports P1 to P8, antenna ports P11 to P18, and a calibration port P0. The signal ports P1 to P8 are connected to an antenna control unit 4, and the calibration port P0 is connected to a calibration control unit 5. The antenna ports P11 to P18 are connected to the antenna elements 21 to 28 in a one-to-one relationship.

[0014] The calibration circuit 3 includes a mixing / distributing device 30 and eight couplers 31 to 38. Hereinafter, the coupler will be expressed as 3n, the signal port as Pn, the antenna port as P1n, and the antenna element as 2n, where n=1 to 8. In addition, the line connecting the signal port Pn and the antenna port P1n will be expressed as the main signal line Ln, and the line connecting the coupler 3n and the mixing / distributing device 30 will be expressed as the branch line LCn.

[0015] The coupler 3n is provided on the main signal line Ln, and outputs a separated signal, which is a part of the signal flowing through the main signal line Ln, to the mixer / distributor 30 via the branch line LCn. The coupler 3n also mixes the calibration signal output from the mixer / distributor 30 via the branch line LCn into the signal flowing through the main signal line Ln.

[0016] The mixing and distributing device 30 mixes the separated signals output from the couplers 31 to 38 via the branch lines LC1 to LC8 and outputs the mixed signal from the calibration port P0. The mixing and distributing device 30 also distributes the calibration signal input from the calibration port P0 into eight signals and outputs the mixed signal to the couplers 31 to 38 via the branch lines LC1 to LC8. The mixed signal of the separated signals output from the calibration port P0 and the calibration signal input from the calibration port P0 correspond to the calibration signal in this disclosure.

[0017] That is, the calibration circuit 3 outputs the transmission signals input via the signal ports P1 to P8 to the antenna unit 2 via the antenna ports P11 to P18. The calibration circuit 3 outputs the reception signals input via the antenna ports P11 to P18 to the antenna control unit 4 via the signal ports P1 to P8. The calibration circuit 3 separates a part of the transmission signals input via the signal ports P1 to P8 or a part of the reception signals input from the antenna ports P11 to P18. Furthermore, the calibration circuit 3 mixes the separated signals and outputs the mixed signal to the calibration control unit 5 via the calibration port P0.

[0018] The calibration circuit 3 distributes the calibration signal input via the calibration port P0 into eight, and mixes the eight distributed calibration signals with the transmission signal or the reception signal to perform calibration. The transmission signal after calibration is output from the antenna ports P11 to P18. Also, the reception signal after calibration is output from the signal ports P1 to P8.

[0019] The antenna control unit 4 weights the transmission signals and reception signals input and output via the signal ports P1 to P8 to change the excitation state of the antenna unit 2 and control the radiation pattern, that is, to form a beam.

[0020] The calibration control unit 5 calculates at least one of the phase difference and the amplitude between the antenna elements 21 to 28 based on the signal acquired via the calibration port P0. The calibration control unit 5 inputs to the antenna control unit 4 a signal in which at least one of the phase difference and the amplitude has been adjusted based on the difference between the calculated value and an ideal value.

[0021] [2. Calibration circuit wiring pattern] As shown in FIG. 2, the mixer / distributor 30 and couplers 31 to 38 that belong to the calibration circuit 3 are fabricated using microstrip lines on a dielectric substrate.

[0022] The mixing and distributor 30 has a three-stage tournament-type parallel power supply structure, and is configured to branch one line into eight and merge the eight lines into one. The mixing and distributor 30 has two-way distributors D1-D7 arranged at each of seven branching points. The eight lines (i.e., branch lines) LC1-LC8 branched by the mixing and distributor 30 are connected to couplers 31-38, respectively. The line merged into one by the mixing and distributor 30 (hereinafter, merged line) is connected to the calibration port P0.

[0023] In the following, among the seven two-way distributors D1-D7 of the mixed distributor 30, the four two-way distributors D1-D4 directly connected to the branch lines LC1-LC8 are referred to as first-stage distributors. The one two-way distributor D7 directly connected to the merging line is referred to as a third-stage distributor, and the two two-way distributors D5 and D6 located between the first-stage distributors D1-D4 and the third-stage distributor D7 are referred to as second-stage distributors. In this embodiment, the two-way distributor D7 is the two-way distributor arranged in the final stage.

[0024] Wilkinson type single-stage transformers (hereinafter, single-stage transformers) are used for the first-stage distributors D1 to D4. Wilkinson type two-stage transformers (hereinafter, two-stage transformers) are used for the second-stage dividers D5, D6 and the third-stage divider D7. Hereinafter, the lines connecting the two-stage dividers D1 to D7, the lines connecting the first-stage dividers D1 to D4 and the couplers 31 to 38, and the lines connecting the third-stage divider D7 and the calibration port P0 are referred to as connection lines. The connection lines are set so that the impedance Zo is, for example, 50Ω.

[0025] As shown in FIG. 3, the two-stage transformers used as the second-stage dividers D5 to D6 and the third-stage divider D7 include an input transformer section TR1 and a branching section TR2. The input transformer unit TR1 is provided on a junction line that transmits a signal before being branched at the branch unit TR2 or a signal after being mixed at the branch unit TR2. The input transformer unit TR1 is formed with a line width W1 different from the line width Wc of the connection line, and has an impedance Z1 different from the impedance Zo of the connection line. Specifically, the line width W1 of the input transformer unit TR1 is set so that the impedance Z1 is expressed by equation (1). The line length t1 of the input transformer unit TR1 is set to approximately λ / 4, and is appropriately adjusted so as to obtain good characteristics. λ is a wavelength corresponding to the center frequency of the signal transmitted and received by the antenna unit 2.

[0026]

number

[0027] The branching section TR2 has a shape that is wired along the edge of a rectangle. The branching section TR2 has a branch point at the center of one side of the rectangle, and the input transformer section TR1 is extended from this branch point. In the branching section TR2, the side opposite to the side having the branch point is separated at the center of the side, and two separated ends T2, T3 are connected to different connection lines, respectively, and are connected to each other via a resistor Rd. The resistance value of the resistor Rd is set to twice the impedance Zo of the connection line. Like the input transformer section TR1, the branching section TR2 is formed with a line width W2 different from the line width Wc of the connection line, and has an impedance Z2 different from the impedance Zo of the connection line. The line width W2 of the branching section TR2 is set so that the impedance Z2 is expressed by equation (2). The line length t2 of the branching section TR2 (i.e., the length along half of the rectangle) is set to approximately λ / 4, and is appropriately adjusted so as to obtain good characteristics.

[0028]

number

[0029] The one-stage transformers used as the first-stage distributors D1 to D4 have a structure in which the input transformer section TR1 is omitted from the two-stage transformers shown in Fig. 3. However, the line width W2 of the branch section TR2 is set so that the impedance Z2 is expressed by equation (3). The line length t2 of the branch section TR2 is set to approximately λ / 4 and is appropriately adjusted so as to obtain good characteristics.

[0030]

number

[0031] In other words, the first-stage dividers D1 to D4 can be made smaller than the second-stage dividers D5 to D6 and the third-stage divider D7 by the amount that the input transformer section TR1 is omitted. Next, the wiring pattern around the first-stage distributors D1 to D4 will be described with reference to Fig. 4. In the following, i=1 to 4, p=2i-1, and q=2i.

[0032] The two branch lines LCp and LCq branched by the 2-way splitter Di are each terminated by a termination resistor Rt. Couplers 3p and 3q are provided in the lines extending from the 2-way splitter Di to the termination resistor Rt. For example, a 50 Ω terminator can be used as the termination resistor Rt.

[0033] The coupler 3p includes a first coupled line Cp1 and a second coupled line Cp2. The first coupled line Cp1 is a portion having a line length of about λ / 4 provided on the main signal line Lp connecting the signal port Pp and the antenna port P1p. Patterns for attaching connectors for attaching and detaching coaxial cables may be provided around the end of the main signal line Lp that serves as the signal port Pp and the end of the main signal line Lp that serves as the antenna port P1p.

[0034] The second coupled line Cp2 is a portion provided in the branch line LCp and has a line length of approximately λ / 4. The first coupled line Cp1 and the second coupled line Cp2 are arranged close to each other with a predetermined interval (e.g., 0.4 mm) between them to form a Wiggly Coupler structure. That is, the adjacent sides of the first and second coupled lines Cp1 and Cp2 each have a triangular wave-like uneven shape, and the uneven shapes are formed so as to mesh with each other. Note that the uneven shape of the adjacent sides of the first and second coupled lines Cp1 and Cp2 is not limited to a triangular wave shape, and may be, for example, a sine wave shape.

[0035] The coupler 3q has a pattern shape that is symmetrical to that of the coupler 3p, and therefore its description will be omitted since it has the same configuration as the coupler 3p. However, in the description of the coupler 3p, the symbol p is replaced with the symbol q.

[0036] [2. Measurement] FIG. 5 shows the results of VSWR characteristics at three terminals calculated by simulation for a single-stage transformer and a single-stage transformer.

[0037] The single-stage transformer was set to W2 = 0.8 mm, t2 = 12 mm, and the two-stage transformer was set to W1 = 1.9 mm, t1 = 9 mm, W2 = 1.1 mm, t2 = 14 mm.

[0038] With a single-stage transformer, in the range of 3.4 GHz to 5 GHz, the VSWR characteristics as viewed from the branch line side (T12, T13 in Figure 5) are 1.15 or less, but there are some areas where the VSWR characteristics as viewed from the merging line side (T11 in Figure 5) exceeds 1.2.

[0039] With the two-stage transformer, in the range of 3.4 GHz to 5 GHz, the VSWR characteristics as viewed from the merging line side (T21 in Figure 5) are 1.15 or less, but the VSWR characteristics as viewed from the branching line side (T22, T23 in Figure 5) exceed 1.2 over a wide range.

[0040] In other words, if a single-stage transformer is used for all of the two-way distributors D1 to D7 that form the mixing distributor 30, the VSWR characteristics as viewed from the merging line side (i.e., the calibration port P0) will deteriorate, and there is a risk that the quality of the signal input / output via the calibration port P0 will be insufficient.

[0041] In addition, if two-stage transformers are used for all two-way distributors D1 to D7 forming the mixing distributor 30, the VSWR characteristics seen from the merging line side are improved, but there is a risk that the VSWR characteristics seen from the branching line side may deteriorate. Furthermore, a two-stage transformer requires a larger space than a one-stage transformer.

[0042] 6 shows the results of calculating VSWR characteristics by simulation for a comparative example in which all two-stage transformers are used for the two-way dividers D1 to D7 that form the mixing distributor 30. The VSWR characteristics were calculated for each of the branch line side (i.e., the couplers 31 to 38 side) and the merging line side (i.e., the calibration port P0 side). The characteristics on the branch line side show the average characteristics of the eight branch lines LC1 to LC8.

[0043] In Figure 6, in the range of 3.4 GHz to 5 GHz, the VSWR characteristics as viewed from the branch line side are 1.2 or less, but there is a large fluctuation, and the VSWR characteristics as viewed from the merging line side (i.e., calibration port P0) are less than 1.5 except for a part around 3.4 GHz.

[0044] FIG. 7 shows the simulation results of the embodiment. In the embodiment, single-stage transformers with excellent VSWR characteristics on the branch line side are used as the first-stage distributors D1 to D4 directly connected to the branch lines, and two-stage transformers with excellent VSWR characteristics on the merging line side are used for the second-stage distributors D5 to D6 and the third-stage distributor D7.

[0045] In Fig. 7, in the range of 3.4 GHz to 5 GHz, the VSWR characteristics as viewed from the branch lines LC1 to LC8 are 1.15 or less, and fluctuations are suppressed compared to the case of Fig. 6. Also, the VSWR characteristics as viewed from the merging line side (i.e., the calibration port P0) are suppressed to 1.5 or less over the entire range of 3.4 GHz to 5 GHz.

[0046] 8 shows the results of actual measurements of the embodiment. In the range of 3.4 GHz to 5 GHz, the average VSWR characteristics as viewed from the branch lines LC1 to LC8 side is 1.25 or less, and the VSWR characteristics as viewed from the calibration port P0 is 1.45 or less.

[0047] [3. Effects] According to the embodiment described above in detail, the following effects are achieved. (1) In the mixer / distributor 30 connecting the calibration port P0 and the couplers 31-38, one-stage transformers are used as the first-stage distributors D1-D4 directly connected to the couplers 31-38, and two-stage transformers are used as the second-stage distributors D5, D6 and the third-stage distributor D7. As a result, it is possible to improve the VSWR characteristics seen from the calibration port P0 side while maintaining the VSWR characteristics seen from the branch lines LC1-LC8 side. In other words, it is possible to improve the quality of signals input / output via the calibration port P0, and as a result, it is possible to improve the calibration accuracy of transmitted / received signals in the antenna device 1.

[0048] (2) In the antenna device 1, the calibration circuit 3 is configured with a microstrip line. This makes it easier to terminate the branch lines LC1 to LC8 than when a triplate line is used.

[0049] (3) In the couplers 31 to 38, the first coupled line Cn1 and the second coupled line Cn2 form a Wiggly Coupler structure. This makes it possible to improve the coupling state of the first and second coupled lines Cn1, Cn2, and to improve the directivity in the couplers 31 to 38. In other words, it is possible to make it difficult for the calibration signal input from the calibration port P0 to be output from the antenna ports P11 to P18, that is, to increase the loss of the calibration signal traveling from the calibration port P0 to the antenna ports P11 to P18.

[0050] [4. Other embodiments] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms.

[0051] (a) In the above embodiment, two-stage transformers are used as the second-stage distributors D5 and D6, but single-stage transformers may also be used. (b) In the above embodiment, the mixer / distributor 30 has a three-stage tournament-type parallel power feed structure, but the tournament-type parallel power feed structure may be two stages or four or more stages.

[0052] (c) Multiple functions possessed by one component in the above embodiments may be realized by multiple components, or one function possessed by one component may be realized by multiple components. Also, multiple functions possessed by multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Also, part of the configuration of the above embodiments may be omitted. Also, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments. [Explanation of symbols]

[0053] 1...antenna device, 2...antenna section, 3...calibration circuit, 4...antenna control section, 5...calibration control section, 21-28...antenna element, 30...mixing distributor, 31-38...couplers, C11-C81...first coupled line, C12-C82...second coupled line, D1-D7...2-way distributor, LC1-LC8...branch line, L1-L8...main signal line, P0...calibration port, P1-P8...signal port, P11-P18...antenna port, Rd...resistor, Rt...termination resistor, TR1...input transformer section, TR2...branch section.

Claims

1. A mixing and distributing device configured to form a two or more stage tournament type parallel power supply structure using a plurality of two-way distributors; a plurality of couplers provided on a plurality of branch lines branched by the mixer / distributor, the couplers being configured to separate a part of a signal flowing through a main signal line, the main signal line transmitting signals transmitted and received by a plurality of antenna elements forming an array antenna, or to mix a calibration signal into the signal flowing through the main signal line; Equipped with The mixing and distributing device includes: a Wilkinson type single-stage transformer is used as the two-way distributor that is disposed in a first stage of the tournament type parallel power supply structure and connected to the branch line, A Wilkinson type two-stage transformer is used as the two-way splitter that is disposed in the final stage of the tournament type parallel power supply structure and connected to the junction line that is joined together by the mixing splitter. Calibration circuit.

2. 2. A calibration circuit according to claim 1, comprising: The mixer / distributor, the multiple couplers, the main signal line, the branch line, and the merging line are made of microstrip lines. Calibration circuit.

3. 3. A calibration circuit according to claim 2, comprising: The coupler includes: the branch line is disposed adjacent to the main signal line, The adjacent portions of the main signal line and the branch line each have a concave-convex shape, and the concave-convex shapes are formed so as to mesh with each other. Calibration circuit.

4. A plurality of antenna elements forming an array antenna; A calibration circuit; Equipped with The calibration circuit includes: A mixing and distributing device configured to form a two or more stage tournament type parallel power supply structure using a plurality of two-way distributors; a plurality of couplers provided on a plurality of branch lines branched by the mixer / distributor, the couplers being configured to separate a part of a signal flowing through a main signal line from each of the main signal lines transmitting signals transmitted and received by the plurality of antenna elements, or to mix a calibration signal into the signal flowing through the main signal line; Equipped with The mixing and distributing device includes: a Wilkinson type single-stage transformer is used as the two-way distributor that is disposed in a first stage of the tournament type parallel power supply structure and connected to the branch line, A Wilkinson type two-stage transformer is used as the two-way splitter that is disposed in the final stage of the tournament type parallel power supply structure and connected to the junction line that is joined together by the mixing splitter. Antenna device.

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